The present invention relates to a semiconductor sensor and a manufacturing method thereof. More particularly, the present invention relates to a semiconductor sensor, the sealing insulating section of which is characteristic, and also the present invention relates to a manufacturing method thereof.
There has been a conventionally known semiconductor acceleration sensor in which a central board and an outside board are laminated on each other so that they are formed into a laminated body, and the central board is subjected to etching as disclosed in Japanese Unexamined Patent Publication No. Hei. 6-82474.
As shown in FIG. 8, the semiconductor sensor includes a central board 1', outside boards 2' and a sealing section 3'. Further, the central board 1' includes a movable electrode section 11'. On the other hand, the outside board 2' includes a stationary electrode section 21'. Furthermore, voltage is impressed upon between the movable electrode section 11' and the stationary electrode section 21' from an external circuit not shown in the drawing. Due to the above arrangement, when the movable electrode section 11' is given a force and displaced by the action of acceleration, an electrostatic capacity between the movable electrode section 11' and the stationary electrode section 21' is changed, and this change in the electrostatic capacity is detected by an external circuit. Therefore, the acceleration can be measured.
The semiconductor acceleration sensor is advantageous as follows. In the case of the semiconductor acceleration sensor, when the thickness of a sheet of Pyrex glass 3' is made thick, that is, when the thickness of a sheet of Pyrex glass 3' is made to be 5 to 10 .mu.m, the electrostatic capacity between the boards 15', 25', which are opposed to each other via the sheet of Pyrex glass 3', can be sufficiently reduced compared with the electrostatic capacity between the movable electrode section 11' and the stationary electrode section 21'. Therefore, sensitivity of the acceleration sensor can be enhanced. However, there are several points to be improved in the above semiconductor acceleration sensor. That is, in order to make the thickness of the sheet of Pyrex glass 3' to be 5 to 10 .mu.m by means of vapor deposition of spattering, it takes a very long time, for example, it takes 5 to 10 hours.
Further, in the above acceleration sensor, although it is possible to reduce the electrostatic capacity between the boards 1' and 25', it is impossible to completely avoid an influence of this electrostatic capacity. Furthermore, due to the difference between the thermal expansion coefficient of silicone (Si) board and that of sealing glass, there is caused a problem in which the temperature characteristic is deteriorated.
Furthermore, the following problems may be encountered. When anode junction is conducted in the process of manufacturing, it is necessary to impress voltage between both Si boards 1' and 2'. Due to an electrostatic attraction force of the impressed voltage, the movable electrode section 11' is drawn and deformed. Accordingly, there is a possibility that both electrode sections 11' and 21' are short-circuited. Therefore, it is difficult to apply a higher voltage. Accordingly, it is difficult to conduct anodic bonding.
Furthermore, in the conventional acceleration sensor, no consideration is given to electromagnetic noise. Especially, when electromagnetic noise is given from the outside of the acceleration sensor, it is impossible to prevent its influence.